For a long time, there has been controversy over whether Kitab Salim ibn Qays was a real person and over the authenticity of his historical-theological hadiths in Islamic and especially Shiite sources. Proponents of the authenticity of Salim’s book have attempted to verify the authenticity of the book by relying on the affirmative opinions of previous thinkers, often regardless of the problems in the content of the book as well as the diverse and confusing manuscripts of the book. Yet, Muhammad ibn Ibrahim Nu'mani’s opinion, a Shiite scholar or transcriber in the fourth century AH, is very important in this regard for several reasons. There are six narrations about Salim, as well as a confirmative sentence about him and his book in Al-Ghaybah’s book. It is necessary to examine the originality of Nu'mani's affirmative sentence in al-Ghaybah’s book. The present study shows that according to the evidence, the affirmative text about Salim and his book—whether added to the fourth chapter of Nomani's book inadvertently or otherwise—is fictitious.